My 6GT AR-10

[Bobby Ball]

Just thought I would share my recent project that I've been working on.

I've had this rifle for quite some time now and when the barrel finally gave up I felt like I wanted to do something different. I've recently started competing in some PRS matches and thought it might be fun to see what I could do with my gas gun, so I decided to go with 6GT for my cartridge choice.

The rifle started life as an Armalite AR-10T with a 24" kreiger barrel. And no matter how hard I tried I just couldn't get the performance out of it that I felt like it was capable of. And for that reason I've been on this mission to make this thing shoot the way I think it should. So starting with the barrel, I ordered a Bartlein blank and a Lija barrel extension. I took the time to smooth and polish the extension and then took everything to my well trusted friend and gunsmith (as I don't have my own lathe yet) to get cut and chambered. We had decided to go with a 24" length and turned the shoulder for the gas block to rifle+1. I was beyond happy with the job. But, one thing we found along the way that wasn't until about 100 rounds went through was that with the eld-m's I had no problem chambering and cycling, but when my big lot of bergers came in they would refuse to feed.
The culprit turned out to be the bevel around the back of the chamber. It was a standard bevel nothing really wrong except what would happen is the red tips of the eld's would deflect just enough to help it kick itself into the chamber. Once I started loading the solid tipped bergers they would stop dead in their tracks straight into the back of the barrel just below the bevel. We took it back off and reprofiled the bevel and problem solved.

As much as I love my Armalite, it is painful to try and find compatible parts at times. But I did manage to find a barrel nut and handguard that I liked and would work from Odin Works. I also ordered an Area 419 arca rail for the bottom of the handguard which I have been very happy with.
Other upgrades on the list are:
SJC Titan muzzle brake
Odin Works adjustable gas block
Odin Works adjustable buffer
Ambidextrous safety
Radian raptor charging handle
Magpul PRS gen 3 stock
Ergo vertical super grip
And a tract toric scope and mount
I'm currently still running the factory match trigger that I spent a fair amount of time smoothing and tuning, but I think it's going to be replaced soon with a TT diamond.
And then full Cerakote that we did in house

I'm currently working on load development with 109 bergers and varget, CCI 450, and I have alpha brass but I have not started using it yet.
I know I'm missing a bunch of things but I'll try to keep it updated if anyone is interested.
I have many more photos of the process and project that I'll continue to add.
Thanks

 

[codym]

Please do, I have gap 10 in 6gt on order. Interested to see how yours turns out

 

[loclass]

Nice looking rifle!

I've been shooting PRS with a 6 GT gasser for just over two years. Mine is built on an Aero M5E1 upper and lower with a GA chambered 22" Bartlein. It's been a fantastically accurate and easy to shoot rifle.

I had the opposite feeding problem in the beginning. Mine would snap tips off the 109 eldm and they would find their way into the lower and lock up the gun occasionally. Polishing feed ramps solved the problem. I eventually went away from the eldm and settled on 107 SMK.

 

[JR1200W3]

Just thought I would share my recent project that I've been working on.

I've had this rifle for quite some time now and when the barrel finally gave up I felt like I wanted to do something different. I've recently started competing in some PRS matches and thought it might be fun to see what I could do with my gas gun, so I decided to go with 6GT for my cartridge choice.

The rifle started life as an Armalite AR-10T with a 24" kreiger barrel. And no matter how hard I tried I just couldn't get the performance out of it that I felt like it was capable of. And for that reason I've been on this mission to make this thing shoot the way I think it should. So starting with the barrel, I ordered a Bartlein blank and a Lija barrel extension. I took the time to smooth and polish the extension and then took everything to my well trusted friend and gunsmith (as I don't have my own lathe yet) to get cut and chambered. We had decided to go with a 24" length and turned the shoulder for the gas block to rifle+1. I was beyond happy with the job. But, one thing we found along the way that wasn't until about 100 rounds went through was that with the eld-m's I had no problem chambering and cycling, but when my big lot of bergers came in they would refuse to feed.
The culprit turned out to be the bevel around the back of the chamber. It was a standard bevel nothing really wrong except what would happen is the red tips of the eld's would deflect just enough to help it kick itself into the chamber. Once I started loading the solid tipped bergers they would stop dead in their tracks straight into the back of the barrel just below the bevel. We took it back off and reprofiled the bevel and problem solved.

As much as I love my Armalite, it is painful to try and find compatible parts at times. But I did manage to find a barrel nut and handguard that I liked and would work from Odin Works. I also ordered an Area 419 arca rail for the bottom of the handguard which I have been very happy with.
Other upgrades on the list are:
SJC Titan muzzle brake
Odin Works adjustable gas block
Odin Works adjustable buffer
Ambidextrous safety
Radian raptor charging handle
Magpul PRS gen 3 stock
Ergo vertical super grip
And a tract toric scope and mount
I'm currently still running the factory match trigger that I spent a fair amount of time smoothing and tuning, but I think it's going to be replaced soon with a TT diamond.
And then full Cerakote that we did in house

I'm currently working on load development with 109 bergers and varget, CCI 450, and I have alpha brass but I have not started using it yet.
I know I'm missing a bunch of things but I'll try to keep it updated if anyone is interested.
I have many more photos of the process and project that I'll continue to add.
ThanksView attachment 8758004View attachment 8758003View attachment 8758005

I appreciate your post. I went through a similar experience. Had a gunsmith/ friend put a 6.5 CM Mullerworks barrel in a SP10 that I built up for PRS. I was planning on shooting 140 Hybrids but found that the Hybrid bullet shape was too skinny for the barrel extension. Most large frame extensions are made for 308. The feed ramps have too much material removed and the bullet drops down in between the lugs and stabs the breech. We opted to find a bespoke extension that was made for 22 Creedmoors. The feed ramp is very steep and has minimal material removed so the bullet tip aims upward as the case rides the ramp and extension. I thought about beveling the chamber/ breech but that removes material around the web and could potentially make the cases more sensitive to high pressures. In other threads, you can see Geisselle cut mini-feed ramps in the breech. Ostensibly due to the same issue. Hybrid and VLD bullet shapes in large frame ARs require some pretty specialized barrel extensions and no one makes them.

If I had it to do again, I would have gone for a 25GT.

 

[matt33]

That's a really cool project. Personally, I go with what I know works, but if everyone had my mindset, there would be no advancement. Please keep us updated.

 

[NHPiper]

Following

 

[Bobby Ball]

The way we re-beveled the chamber face we kept the case supported entirely just like it was originally. ill attach this photo to help explain. So if you look at the blue top cheesy diagram I quickly drew. We beveled the angle out instead of the green example which would have taken more out.

 

[LRRPF52]

When I was spec’ing out my .260 Rem build and looking at which bullets I would shoot, everyone told me to avoid Berger VLDs because of their tendency to not feed.

I had GAP do the work on it, starting with a Bartlein pipe and asked them to spec the chamber/throat for my sized 7mm-08 Winchester cases and 139gr Scenars. It feeds everything fine, including Hornady tipped bullets, Berger VLDs (pre-hybrid), SMKs, whatever.

I like 130gr old school VLDs through it the most I think, but it cuts ragged small holes with 139gr Scenars and 142gr SMKs as well. It’s really flat to 1000 with 130gr VLDs in practice. I shot 3” groups with it at 500m at a range in Finland before one of the Sniper Competitions there, with 130gr VLDs.

My buddy, who is an exotic alloys medical device engineer and gunsmith (put himself through 2 different gunsmithing programs during his engineering degree) bought a bunch of ArmaLite AR-10s about 12 years ago and ended up doing dual feed ramps for the .260 Rem. He cut careful little feed ramps into the feed cone in the breech, as well as tuning-up the barrel extension feed ramps. These were all AR-10Bs with the steel M14 style mags.

Looking at things today, I think a smaller frame chambered in 25 GT spitting 133-135gr with a lighter BCG would be the ticket, using the Savage MSR-10 action or maybe smaller like an SFAR. That should be a combo of minimal sight picture disturbances and maximum velocity and BC, without stepping up to 7mm and larger case volume. You know when you hit the plates at distance with the new class of 25 cals in the 130gr+ range, unlike with 6mm.

 

[Bobby Ball]

Ill agree on that. 25 GT has definitely caught my eye. I've been a bit of a fan of quarter bore for a while now.
I'm running an AR-10B and the magazine thing is one of my bigger hangups with the platform. It's a real pain to get magazines. And I forgot to mention above but I found that my B magazines didn't have any anti-dive followers. So I took them out of some type-A magazines that I had laying around. Fortunately for any DPMS platform guys going this route that shouldn't be as much of an issue.

Doing what I've done so far and having built other gas guns in non-standard calibers, the most challenging hurdle that I feel like I've seen so far is the lack of options in the barrel extensions. I built an 8.6 Blackout for a customer last year and it had a very nice large center feed barrel extension on it that had zero chambering issues. Between that and this project and some of the other calibers I've done, it makes me think that there are other barrel extension designs that could be done and work substantially better with today's more modern cartridge designs. A lot of times I think a lot of the mentality in this industry is more of an if it ain't broke don't fix it mindset. Or a that's good enough mindset. And that really just doesn't work for me.